paragraph4
.0em plus.0ex minus.2ex-.5emNotations: Let's define \(I\)  as the input image, \(\mathcal {F}(I)\)  the backbone features from the image encoder. Let \(\mathcal {Q}(\cdot )\)  be the function that yields a region embedding \(\mathbf {r}_b\)  from \(\mathcal {F}(I)\)  and a given box region proposal \(b\) , which involves FPN [1]}, ROI-Align [2]}, and Faster R-CNN head [3]}. We have:
\(\mathbf {r}_b = \mathcal {Q}(\mathcal {F}(I), b)\) 
